Sorry if this sounds like a newbie question, but am I correct in thinking that open dumps (downpipes) replace testpipes or cats on a turbo setup?

 

Open dumps allow your waste gates to vent to atmosphere rather than vent into your exhaust. Wikipedia/Search is your friend.

<<---- Has dump tubes.

 

he might be talking about open exhaust, or cutouts, which if so, could be fabricated to replace the cats.

 

^^ Good point. Though i haven't heard of many Z owners running dual cutout's on a "turbo set up" like he mentioned???

 

Dual cutout's would be interesting. It would def save people alot of money on buying a true dual 3" exhaust when you could prob get away with using stock exhaust and cut outs. Anyone out there using cutouts ?

 

im using one on my single turbo.

it would be ideal to run 2 on a twin setup, one on each exhaust.

 

just curious....how does it sound?

 

stock exhaust with dump tubes would really hurt your spool time unless you were running really low boost.

downpipes= the area right after the turbo's
dump tubes= atmosheric dumped wastegates
testpipes= deletion of cats (thats why they are called "testpipes" only supposed to be used for testing a bad cat)

hope that clears it up.

 

Can you elaborate on this? Is it because of the restrictiveness (is this even a word?) of the stock exhaust?

 

You would think if the cut out's were put in right where test pipes would be that the stock would have no effect because when cut out's are open the entire stock exhaust is bypassed, just a thought.

 

i ran a catless downpipe on my previous car with an electric cut out...with one push of a button the cutout opens. without proper tuning it might hurt your performance. sounded loud as hell though.

 

it will help when they are open, but hurt TILL they open. most of your driving will be happening with the wastegates closed, and performance in that area will suffer.

the peak numbers on a dyno might look good, but it will be crappy in low and mid range.

 

listen to Alberto's car he has open dumps and his car sounds mean as $hit.

https://my350z.com/forum/forced-induction/232367-fi-video-and-pic-thread.html

its the 7th post, the blue 350z, listen to his vids for a good example of open dumps.

 

There are two videos on our myspace page taken while we tuned an APS TT. One video with the cutouts open, one closed with the stock exhaust. It really sounds awesome! We used QTP electric cutouts and we could actually vary how open the cutouts were. Its gives a little tunability to the sound of the exhuast.

http://www.myspace.com/functiontuned

 

im running mine with the stock exhaust and its electric, you can open it a little or a lot. it doesnt really affect my spool up, but im only running 10psi.

atp sells one that is boost activated, it has an actuator just like an internal wastegate and runs off a boost signal.

and when its open, its really really loud, drones quite a bit, but since its about a foot from the turbo, the turbo sounds awesome, you can hear it spool up, sounds like a jet engine when i get on it.

 

I have open dumps and is the best combo if you have F/I... btw where is the guy that used to sell the dumps for greddy kit? my brother wants them but I can't find him anywhere... Thanks!

 

that blue car with the yellow overlays has insanely fast spool